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ROTO 50 V2 benchtest review

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Old 04-04-2007, 12:48 PM
  #1
Sandman Norway
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Default ROTO 50 V2 benchtest review

What a nice engine this is :-) Beautifully made, quality fee, overall NICE..

Starts really easy, but needs some flipps to draw fuel trough a dry line, but once wet, fired up easy..
Was a bit rough at low-to-mid range, some fiddling with the low-end needle did help, but still to mutch vibes
at the low end. This is proberly due to new engine, and hopefully be better..

Ran it slow and easy with a APC 19x8W a full tank, 400ml. THAT took some time :-) Gave it initially a few, 2 minutes run, let i cool down, and the new 2 min. run. Next tank of fuel, I ran it over the powerband, but not WOT. Did some minor adjustments to Low and High needles to improve the transitions, mutch better, but still not Flyworthy.. Tank 3, now I ran it harder, but still with the 19x8W, tacked it inn at 8000+ RPM, but didn't run more that a few sec. On VERY nice feature is a LED lamp, that blinks at 1\2 RPM, and will after the engine is stopped blink at the max RPM during the last run.. This very nice.. I hate to stand close to a APC at 8K fiddling with my taco.. Every gasser should have this feature.. After tank 3, i switched to a Mens Ultra 22x10, this gives 6700 RPM. Pretty good, consider new engine and 3% oil..

Now, the downsides.. The ignition box was surprisingly big , not a problem, but my other gasser ZDZ 60, has a box half the size.. OK, so this is a twin, that may call for bigger heatsink on the switchtransistors.. The right sylinder gets 30 deg C warmer than the left, this may be normal, but what I`m conserned about is that i have fluid oil deposit from the left mufler pip, but the right one is dry. This may be the result of raised temp in the right burns the oil, or the lack of oil in right cylinder raises the temp... Not happy about this.. The plugs has the same nice light brown color.. Strange... Anyone has an input to this..?????

Next, it was not easy to mount this engine. Most pictures show this engine with a wide base, but my engine did not have this, more a flush flange. Thankfully I have my own lathe, so I made up some stand off`s, but I would prefer a wider base to distribute the force..
The carb is mounted in a strange way, I would prefer to have it turned 90 degres, for easyer mounting. As this is a rear carb engine, it is often needed to open the firewall up, with the carb trough it. By "sideways" mounted carb, the hole has to be wide..

The carb need some work.. Both the choke and throttle plate has holes in them, They should be soldere shut. This will make the choke more effective, and it would be possible to stop the engine with the throttel trim. If closed, the engine will keep ideling..


The downsides I find is "little" thing, but the raised temp\lack of oils is concerning me..

I will "play" some more with it tomorrow. I like to run it, and tune it close to perfection on a bench before I mount it on a bird.
This nice little twin, will be tested in a GP Pitts... It will be tight, but it should fit in the cowl....

PS: When this engine is out of the Rough spot at low RPM, its a smoot as glass.. The vibes from this twin, is non exsisting..
If I may get the low end vibes tamed, this will be a VERY nice engine..
The weight of the engine, ignition, and pitts style mufflers are 2160 grams... And it sips fuel, it drank only 200ml over 20 min, with
throttle between 3-6k RPM....


I`ll give a better review after it has been tested In Air...

Best regards, and Happy Easter..

Sandman

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Old 04-05-2007, 07:44 AM
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Default RE: ROTO 50 V2 benchtest review

Did two more tanks today, total of 800ml. And the temp on the cylinders are now within 10 degrees C. And there is liquid oil
resdues from both muffler pipes.. It`s transistion is now improving, but it stil has a rough spot around 25-2700.. Hope this will fade out after some more running time. The engine has now seen aprox 2 liter of gas... I have not leaned out the high end, and it still tac the Mens Ultra 22x10 at 6700... Will start to lean it out after another 2 liters of gas..
Starting is easy, but I still need to solder the two holes in the choke and throttle plates..

Soon its time to fly this puppy... That will be fun...


Regards..

Sandman
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Old 04-08-2007, 06:30 AM
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Sandman Norway
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Default RE: ROTO 50 V2 benchtest review

A little update... Most of my vibes at 2500 RPM, was due to a poor design on the bench mount. My fault..
After making a new fixture for the engine, this shake is now gone.. Still has a rough spot on the throttle curve, but
this is to be expected, I`m told..

So I`ll give it a few more tanks on the bench, then it is to be mounted to my GP Pitts...

I`m very happy about this little engine..


Best regards..

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